The reliable sequence
Quick start: solve a 2D structure from beginning to end
Follow this order for a new frame or truss model.
- 1Start with Model Setup
Choose a blank model or template, working units, grid spacing, and default member behavior.
- 2Create connected geometry
Place nodes, draw each member from start i to end j, and split crossing members where force transfer is intended.
- 3Assign supports and member behavior
Restrain the necessary global degrees of freedom and confirm frame, pin-ended, or released-end behavior.
- 4Assign material and section properties
Every member needs suitable E, A, and I; self-weight also needs section area and material density.
- 5Apply loads and choose a scenario
Add signed nodal or member loads, configure cases or combinations, and select what the next analysis should solve.
- 6Run and inspect results
Resolve model-health warnings, then review reactions, displacements, deflected shape, and member forces.
- 7Verify, save, and report
Check equilibrium and expected behavior, save a recovery point, and export a report from the latest analysis.
A downward global nodal or member load is negative. Read the complete 2D sign and axis convention before applying loads.
When to use this workspace
Plane frames, trusses, and mixed structures
Use the 2D workspace when multiple members connect through nodes and the model needs axial response, frame bending, end releases, or two global force directions.
Geometry and canvas
Set up, draw, and edit the structure
- 1Open Model Setup
Choose a blank canvas or a portal, braced frame, gable frame, triangular truss, Pratt truss, or Warren truss template. Set units, grid spacing, and default member behavior.
- 2Place nodes
Select Node and click the grid. For exact geometry, select a node and edit its X and Y coordinates in Properties.
- 3Draw members
Select Member, choose the start node, then the end node. Local +x follows this start-to-end direction.
- 4Edit selections
Use Select for one or multiple items, then move, duplicate, copy/paste, or edit. Deleting a node can also remove connected entities.
- 5Navigate without changing the model
Pan, zoom, Fit, Focus mode, and Display options change the view only. A load display filter does not change the active analysis scenario.
Members transfer force through shared nodes. Split both members and connect them to the same node when an intersection should be structural.
Restraints and stiffness
Supports, member behavior, materials, and sections
Supports and nodal restraints
Use Custom to toggle Ux, Uy, and Rz individually. Support restraints use global axes, not member-local axes.
Frame members, pin-ended members, and releases
Transfers axial force, shear, and bending. End rotations remain connected unless Start Rz or End Rz is released.
Both end rotations are released. With joint-only loading it reproduces ideal truss axial response.
A span load on a pin-ended member can still create local shear, bending, and deflection within the member. For an ideal truss, convert gravity or span loads to equivalent joint loads.
Materials and sections
| Input | Purpose | Canonical model unit |
|---|---|---|
E | Elastic modulus for axial and flexural stiffness | GPa internally |
Density | Mass density used to generate self-weight | kg/m³ internally |
A | Area used for EA/L axial stiffness and self-weight | mm² internally |
I | Second moment used for frame bending stiffness | mm⁴ internally |
Create reusable model materials and sections, assign them to selected members, or import a standard steel section from the available regional catalogues. Confirm that A and I represent the intended section orientation and bending axis.
Loading
Apply loads, cases, combinations, and self-weight
Ordinary loads
Nodal load
Apply global Fx, Fy, and Mz directly to a node.
Member point load
Enter position from the member start, force components, and local or global axes.
Distributed load
Enter start/end positions, start/end intensities, and a local-x, local-y, global-X, or global-Y direction.
A displayed arrow follows the signed direction. Loads may remain unassigned for a simple All Loads model.
Load cases, categories, and combinations
- Create a case and choose a category such as dead, live, wind, or another project classification.
- Assign loads to that case. Unassigned loads remain in the All Loads scenario.
- Create a combination with category factors or specific-case factors.
- Choose the analysis scenario in the app bar before running.
Do not include the same case through both its category factor and a specific-case factor. The interface blocks conflicting combinations.
Structural self-weight
Enable self-weight in a load case, set its multiplier and gravity direction, then confirm every included member has a section area and material density. Self-weight is generated from density × area × gravity.
- Default gravity acts downward in global Y.
- A member with missing or zero density is skipped and produces a warning.
- Self-weight on pin-ended members acts along the spans; use joint equivalents for an ideal truss.
- Check combinations for repeated self-weight from more than one case.
Analyze and interpret
Run and review the 2D model
- 1Check model health
Resolve missing geometry, disconnected nodes, unstable restraints, unsupported nodal moments, invalid properties, and unintended crossings.
- 2Select the scenario
Choose All Loads, one load case, or one combination. Results and reports use the scenario from the most recent analysis.
- 3Run analysis
The solver assembles the linear stiffness system. A mechanism or near-mechanism produces an error or conditioning warning.
- 4Use canvas result views
Switch among reactions, deflected shape, axial, shear, and moment. Diagram scale changes only the visualization.
- 5Use tables for exact values
Reactions list Rx, Ry, and Rm; Displacements lists Ux, Uy, and Rz; Members gives governing values; Stations reports x, x/L, N, V, M, and displacement.
- 6Inspect members
Select a member or plotted metric to check end actions, peak locations, and local response together.
Use it to understand behavior, not to measure displacement from the canvas. Read magnitudes from the results tables.
2D Structural Analysis reference
Sign and axis conventions
+X is right, +Y is up, and +Mz/+Rz is counter-clockwise. Nodal loads, supports, reactions, and displacements use global axes.
| Quantity | Positive (+) | Negative (−) |
|---|---|---|
| Global Fx / Rx / Ux | Right | Left |
| Global Fy / Ry / Uy | Up | Down |
| Global Mz / Rm / Rz | Counter-clockwise | Clockwise |
| Member local x | From start (i) to end (j) | From end (j) toward start (i) |
| Member local y | 90° counter-clockwise from local +x | Opposite local +y |
| Member axial N | Tension | Compression |
| Member bending M | Sagging | Hogging |
| Member shear V | +V plotted on local +y | −V plotted on the opposite side |
Fy = −10 kN10 kN downward nodal forceMz = −6 kN·m6 kN·m clockwise nodal momentq = −4 kN/m4 kN/m downward in Global YReversing start i and end j reverses local +x and changes local +y. Use Global Y for a load that must remain vertically downward regardless of member slope.
Keep a calculation record
Save, recover, version, and report a 2D project
Working copy and cloud project
- Local recovery keeps a browser-local copy while you work. It is not a substitute for a cloud save or downloaded backup.
- Save updates the current project; Save As creates a separate project.
- Download source exports the project JSON for backup or inspection.
- Folders organize cloud projects when available.
Activity, versions, and checkpoints
- Activity records supported edits, AI-applied changes, saves, checkpoints, and restores.
- Create a named checkpoint before a major geometry, property, or loading change.
- When a cloud revision conflict appears, either reopen the newer cloud version or preserve the canvas as a separate copy.
PDF report
- Choose the intended scenario and run the latest model.
- Enter report title, project number, author/checker details, and report-specific assumptions.
- Choose the model/result diagrams and individual member summaries to include.
- Export, open, and inspect units, scenario, tables, legends, page breaks, and branding.
Assisted modeling
Use Optimal AI with preview and verification
Ask about the current selection or request a model change. Review the preview before applying it, including target IDs, node coordinates, working units, member orientation, material/section values, load case, axis choice, and load signs.
Example prompt: “On selected node N4, add a 10 kN downward global force.”
Verify every applied entity on the canvas and in Properties, run the deterministic solver, and complete the same checks used for a manually built model.
Verified analysis domain
Assumptions and limits
Included
- Two-dimensional static analysis with global X, global Y, and rotation at each node.
- Axial and Euler–Bernoulli flexural stiffness.
- First-order, small-displacement, linear-elastic response.
- Continuous, one-end-released, and pin-ended members.
- Nodal forces/moments and full, partial, uniform, or linearly varying member loads.
- Local/global load directions, self-weight, linear cases, and user-defined combinations.
Excluded
- P-Delta and other second-order effects.
- Geometric or material nonlinearity.
- Tension-only or compression-only behavior.
- Shear deformation, support settlement, imposed strain, and thermal loading.
- Buckling, modal, response-spectrum, time-history, and other dynamic analysis.
- Section resistance, connection capacity, and code-based member design.
See the Structural Verification Centre and verification plan for the solver’s verification scope.
Work faster
Keyboard shortcuts
Use Ctrl on Windows/Linux or Command on macOS.
Before relying on results
2D model review checklist
Fix common problems
2D Structural Analysis troubleshooting
“The model is unstable” or “unstable near node…”+
The stiffness system has a free rigid-body or mechanism degree of freedom.
- Confirm enough independent support restraints exist in global X, Y, and rotation for the chosen member behavior.
- Check disconnected nodes, zero-length members, accidental releases, and pin-ended chains.
- For a truss, confirm the geometry is triangulated and the supports restrain global translation.
- Add one justified restraint at a time and rerun; do not hide a mechanism with arbitrary stiffness.
A load or reaction points the wrong way+
Global +X is right, +Y is up, and +Mz is counter-clockwise. A downward Global Y load is negative. On inclined members, confirm whether the direction is global or member-local and check the i-to-j orientation.
Crossing members do not transfer force+
Members connect only through shared nodes. Split both members at the intended intersection and make their ends reference the same node.
Results are missing or do not reflect the latest edit+
Confirm every member has valid E, A, and I as required, select the intended scenario, and run again after any geometry, restraint, property, load, or scenario change.
Self-weight is zero or incomplete+
Check positive material density and section area on every included member. Confirm the self-weight case is enabled, its multiplier is nonzero, and the analyzed scenario includes that case.
A pin-ended member shows bending or shear+
A load applied along a member span can create local member bending even when both end rotations are released. For an ideal truss, place equivalent loads at the joints.
A result is many orders of magnitude too large or small+
Check E, A, and I first. Confusing mm⁴ with m⁴ changes frame stiffness enormously. Also check coordinates, load-intensity units, and the active unit labels.
A project cannot be saved or has a revision conflict+
Confirm sign-in and current-plan access. For a revision conflict, save the canvas as a separate copy or reopen the newer cloud revision. Local recovery remains browser-specific and can be lost if site data is cleared.
The PDF fails or is incomplete+
Select the intended scenario, run it, and retry with default branding. Replace an invalid logo and reduce optional member sheets if necessary. Report the browser and exact error if it persists.
Quick reference
2D symbols and terms
- E
- Modulus of elasticity for linear-elastic material stiffness.
- A
- Cross-sectional area used for axial stiffness and self-weight.
- I
- Second moment of area used for member bending stiffness.
- Ux, Uy
- Nodal translations in global X and global Y.
- Rz
- Nodal rotation about the out-of-plane Z axis.
- N, V, M
- Member axial force, shear force, and bending moment.
- Release
- A member-end condition that removes moment transfer for the released rotation.
- Load case
- A named group of loads analyzed alone or included in a combination.
- Combination
- A linear sum of cases or categories multiplied by user-defined factors.
- Local axes
- Member axes: local x from start i to end j, and local y perpendicular to it.
- Global axes
- Model-wide axes shared by nodes, supports, reactions, and global loads.
- Mechanism
- A model with insufficient stiffness or restraints to resist one or more motions.
- Station
- A sampled location along a member where force or displacement is reported.
Responsible use
Analysis supports judgment; it does not replace it.
The user remains responsible for the structural idealization, inputs, load combinations, code requirements, interpretation, independent checks, and decisions affecting safety or construction.